SQL 不同的分组方式

Question

SQL : Group by country & Count, 很简单但我迷路了 我的桌子上有1

Country    | Optin    | 
--------------------------
USA        | 1        |
USA        | 1        |      
GERMANY    | 0        |      
USA        | 1        |          
GERMANY    | 1        |         
JAPON      | 1        |  

我想返回这张表，我只想在 optin part=1 时按国家/地区计数

Country    | Optin    | 
--------------------------
USA        | 3        |
GERMANY    | 1        |
JAPON      | 1        |  


SELECT *
FROM Table1
WHERE Optin = 1
GROUP BY Country

Answer 1

我只想在 optin part=1 时按国家/地区计数

使用COUNT（或SUM，因为所有optin返回= 1）和GROUP BY country：

SELECT Country, COUNT(optin) 
FROM table1
WHERE optin = 1
GROUP BY country;

SQL Fiddle Demo

Answer 2

SELECT  Country, SUM(CASE WHEN Optin = 1 THEN 1 ELSE 0 END) totalOptin
FROM    TableName
GROUP   BY Country

• SQLFiddle Demo